1. Field of the Invention
The present invention relates to a front gear apparatus for a bicycle having a chain restoring device.
2. Description of the Related Art
FIGS. 7a through 7e show a known example of front gear apparatus. This apparatus includes a front gear or chainwheel G1 having a chain restoring device 150 so that a chain 4 having fallen off the chainwheel G1 may be restored on the chainwheel G1 by rotating the chainwheel G1 and operating a front derailleur 6. Specifically, as shown in FIG. 7b, the restoring device 150 includes a chain receiving portion 151 extending axially of the chainwheel G1, and a chain engaging portion 152 extending from the chain receiving portion 151 radially outwardly of the chainwheel G1. When the chain 4 falls off the chainwheel G1, the restoring device 150, in its movement from inside the loop of the chain 4 to outside as the chainwheel G1 rotates, catches an upper run 4b of the chain 4 at the position shown in a solid line in FIG. 7a and raises the upper run 4b of the chain 4 to the position shown in a dotted line. As the upper run 5b is raised to the level of the front derailleur 6, the cyclist operates the derailleur 6 to cause the chain 4 to cross the chainwheel G1. This crossing and rotation of the chainwheel G1 put the chain 4 back on the chainwheel G1 again.
In the prior art noted above, the chain falling from the chainwheel to the restoring device would sometimes fall off the restoring device as a result of vibrations or the like. The chain tends to fall off the restoring device more easily where the chain engaging portion is designed to extend a reduced length from the chain receiving portion for compactness and lightness of the chain restoring device.
Further, as shown in a dotted line in FIG. 7c, if the restoring device 150 is outside the loop of the chain 4 when the chain 4 falls off the chainwheel G1, the restoring device 150 may move into contact with an outside position of the lower run 4a of the chain lying below a crank axle 3. As shown in FIG. 7d, the restoring device 150 has a shape difficult to slip past the lower run 4a of the chain. As the restoring device 150 moves upward after contacting the lower run 4a of the chain, the chain engaging portion 152 begins to act on the lower run 4a of the chain as shown in FIG. 7e. Consequently, the lower run 4a is not easily separable from the restoring device 150 and, as shown in a solid line in FIG. 7c, the lower run 4a becomes caught by the restoring device 150, thereby rendering the chainwheel G1 no longer rotatable.